Arrow Board Modes: What Each Display Means

Arrow board in arrow mode, directing traffic to merge right. Illustration drawn by Safe Pass Traffic; not to scale.

An arrow board is the black panel of flashing yellow lights you see behind a lane closure. It has three modes: an arrow or chevron that tells you which way to merge, a double arrow, and a caution display that warns without directing you to change lanes.

What it means

Section 6L.06 of the California MUTCD 2026 Edition defines an arrow board as a sign with a matrix of elements capable of flashing or sequential displays, giving extra warning and directional information to help drivers merge and move through or around a work zone. The elements shall be yellow and the board shall be finished in non-reflective black. It shall have three mode selections:

Arrow or chevron mode: a flashing arrow, sequential arrow or sequential chevron pointing the way traffic must merge.
Double arrow mode: a flashing arrow pointing both ways.
Caution mode: a flashing caution or alternating diamond display that warns without pointing a direction.

The flashing rate shall be not less than 25 nor more than 40 flashes per minute, and the lamps shall be dimmed for nighttime operation.

The shall rules for each mode

Arrow or chevron mode shall be used only for stationary or moving lane closures on multi-lane roadways.
For shoulder work, blocking the shoulder, roadside work near the shoulder, or temporarily closing one lane on a two-lane, two-way roadway, an arrow board shall be used only in caution mode.
Arrow boards shall only be used to indicate a lane closure. They shall not be used to indicate a lane shift.
When arrow boards close multiple lanes, a separate arrow board shall be used for each closed lane.

What drivers often get wrong

Waiting until the board to merge. The arrow board sits at the start of the merging taper. Merge smoothly when you see it, not at the last cone.
Reading caution mode as a lane closure. On a two-lane road or for shoulder work, the caution display means slow down and watch for activity; it is not telling you to change lanes.
Relying on the board alone. The board works together with signs and channelizing devices. Read the signs that come before it.

Where it goes in a work zone

For a stationary lane closure, the arrow board should be on the shoulder at the beginning of the merging taper. Where the shoulder is narrow, it should be in the closed lane. Either way, it shall be behind the channelizing devices that move traffic out of the closed lane. For mobile operations, it should be far enough from the work to give approaching drivers time to react. A vehicle displaying an arrow board shall have high-intensity rotating, flashing, oscillating or strobe lights.

What contractors need to know

Pick the right board type. Type A suits low-speed urban streets, Type B intermediate-speed roads and maintenance or mobile work on high-speed roads, and Type C high-speed, high-volume projects.
If used, an arrow board should be used in combination with appropriate signs, channelizing devices or other devices shown on the plan, not on its own.
When it is not in use, the board should be removed; if not removed, shielded; or, failing both, delineated with retroreflective devices.
A portable changeable message sign may be used to simulate an arrow board display.

Related signs

Frequently asked questions

Can an arrow board show an arrow on a two-lane road?

No. When one lane of a two-lane, two-way road is temporarily closed, the arrow board shall be used only in caution mode. The arrow or chevron mode is reserved for lane closures on multi-lane roadways.

Can I use an arrow board for a lane shift?

No. Section 6L.06 says arrow boards shall only be used to indicate a lane closure and shall not be used to indicate a lane shift.

What color are arrow board lights?

Yellow. The manual requires the elements to display yellow, on a non-reflective black board.

Sources

Need this sign on a traffic control plan?

Safe Pass Traffic prepares PE & TE stamped traffic control plans, striping plans and typical plans for projects statewide in California, and helps with the permit submittal. We draw the plan that shows where the arrow board, signs and devices go; your contractor or traffic control provider sets them in the field. Call or text (714) 362-1348 or request a quote.